Tooth flank polishing tool

ABSTRACT

The invention relates to a tooth flank polishing tool ( 31 ) comprising a base ( 32 ) that can be rotated about a central axis. A polishing fleece ( 33 ) which can be introduced into at least one tooth gap ( 39 ) of a gear ( 30 ) that is to be polished is mounted on the base ( 32 ). At least some sections of the polishing fleece ( 33 ) have an external contour that is adapted to the shape of a tooth flank ( 37 ). The tooth flank polishing tool can be used for polishing gears ( 30 ) or threads.

The invention relates to a tooth flank polishing tool and the use of such tool.

An important criterion for the quality of tooth gears is the roughness or smoothness of the tooth flanks. Roughness values Ra ranging from 0.4 μm to 1.6 μm can be attained by grinding, which correspond to peak-to-valley heights Rt of 1.6 μm to 6.3 μm; roughness values of Ra=0.2 μm can be attained by vibratory grinding. For vibratory grinding, the work pieces to be worked on are placed as bulk material in a working container, together with abrasive products, so-called chips, and frequently an additive in aqueous solution. A relative movement between workpiece and the abrasive product is produced by an oscillatory and rotational motion of the working container which causes removal of material from the workpiece, in particular on its edges. Vibratory grinding can produce excellent surface smoothness.

Disadvantageously, vibratory grinding can take a long time, between 4 hours and 24 hours. In addition, the size of the components to be worked on is limited with vibratory grinding, because the components together with the chips must fit inside a working container.

Larger tooth gears which are not suitable for vibratory grinding according to the aforedescribed process due to their size, must therefore be worked on manually with fine polishing tools. Disadvantageously, manual processing is unable to produce a uniform surface quality. As a result, some sections on the tools flanks may have different roughness, causing portions of the bearing support surface to be different which can adversely affect the load bearing capacity of the tooth. The sliding properties of any manually polished tooth gear are therefore not uniform over the entire periphery, which may lead to increased wear during operation and increased noise generation.

Another problem when working with fine-grained polishing tools is so-called burning, or overheating during grinding. Burning occurs when abrasive material with very small of fine grain size is used. This is due to the fact that the coefficient of friction between the abrasive material and the workpiece becomes very high with decreasing grain size, with heat generated by friction potentially causing material changes of the workpiece. The material can, for example, become brittle which would adversely affect the service life.

It is therefore an object of the invention to provide a tooth flank polishing tool which is capable of producing tooth flanks with particularly small roughness, in particular on tooth gears that had not been worked on by vibratory grinding, thereby obviating the disadvantages of conventional manual polishing methods, as well as to elucidate various uses for such tooth flank polishing tool.

The device aspect of the object is attained with a tooth flank polishing tool having the features of claim 1. Advantageous embodiments and modifications of the invention are recited in the dependent claims.

According to the features of claim 1, the tooth flank polishing tool has a base which is rotatable about a central axis and on which a polishing fleece, which can be inserted in at least one tooth gap of a tooth gear to be polished, is attached. At least some sections of the polishing fleece have an outside contour that matches the shape of a tooth flank.

The tooth flank polishing tool is used to remove roughness peaks, i.e., the surface structure of the tools flanks is at least partially plastically deformed with very little material removal and hence smoothed. With the tooth flank polishing tool of the invention, a tooth flank can advantageously be polished so smoothly so that it has a very small surface roughness Ra of preferably=0.4 μm, in particular=0.2 μm. In this way, the percentage of the bearing support surface and hence the tooth load bearing capacity is increased and the sliding properties of the tooth gear are improved. The basic geometry of the previously generated tooth gear arrangement is not changed. The damage of the tooth surfaces from thermal overheating, which can occur when fine-grained grinding disks that do not match the geometry of the tools flanks are used, can thus be reliably prevented with proper handling. Advantageously, the tooth flank polishing tool can be adapted to any size of a tooth gear.

With the tooth flank polishing tool of the invention, tooth gears having a very large diameter, i.e., a diameter greater than 1000 mm, can be worked on in order to generate a surface in the region of the tooth flanks which is able to prevent, for example, gray stippiness. Gray stippiness refers to a wear characteristic of regions near the surface of highly stressed metallic components, for example the tooth flanks of tooth gears. Gray stippiness can be identified on dull gray surfaces with the naked eye. The origin is a large number of very small nicks and pores caused by mixed friction and sliding friction and the resulting plastic deformation of regions near the surface. Gray stippiness can eventually cause deep incipient cracks and nicks on the tooth flanks. Another important aspect of the invention is that the tooth flank polishing tool can be integrated in an automated process, so that, unlike with manual surface processing, predetermined surface qualities with the required small variation range can be obtained.

The polishing fleece can be made of a composite material or a single material. Preferably, the polishing fleece includes an organic, synthetic and/or mineral material. Organic materials for a polishing fleece include cotton or sisal. Synthetic or chemical materials for a polishing fleece may be resin fibers, tangled resin fibers or nylon. A suitable mineral material is particularly aluminum oxide (Al₂O₃), preferably in the form of corundum.

In an advantageous embodiment, the polishing fleece is applied at least over sections of a surface of the base. For example, the polishing fleece is attached on the base with an adhesive.

In another embodiment, the polishing fleece is strung over the surface of the base. This requires a clamping device for securing the polishing fleece. Covering the area has an advantage over using an adhesive in that the polishing fleece can be exchanged if needed.

In another particularly advantageous embodiment, the polishing fleece is inserted in a radial circumferential groove or a seat of the base. In this way, the polishing fleece can be permanently and stably affixed.

A combination of the base and the polishing fleece can have the shape of a polishing disk. The tooth flank polishing tool can then advantageously be clamped in conventional polishing machines, such as rotary tables, gear hopping mills or tooth flank grinding machines. Machining is performed incrementally, i.e., the tooth gear is rotated commensurate with its pitch and the tooth flank polishing tool is moved between two tooth flanks.

According to another embodiment, the combination of the base and the polishing fleece can have the shape of a polishing worm gear. With a polishing worm gear, the flanks of the tooth gear can be polished in a continuous process. The polishing worm gear can also be clamped in conventional polishing machines, such as rotary tables, gear hopping mills or tooth flank grinding machines. The polishing fleece hereby formed a tooth of the polishing worm gear or a surface region of the tooth. The tooth can also be formed on the base and the polishing fleece can be attached outside on the tooth.

The combination of the base and the polishing fleece (73, 85, 94) can have the shape of a polishing finger. The polishing finger can be versatilely used. This type of tooth flank polishing tool is suitable for rotary tables and gear hopping mills.

The tool flank polishing tool is primarily intended for polishing tooth gears, for example, spur tooth gears and pinions, spur ring gears, bevel spur gears and pinions, as well as worm gears and shafts, in particular with diameters greater than 1000 mm.

In an advantageous modified embodiment of the invention, the base is at least indirectly coupled with an oscillation generator. The oscillation generator is provided for superimposing on the rotary motion of the base an oscillatory motion. The oscillatory motion occurs in at least one spatial direction, for example in an axial or a radial direction of the base. Also feasible in the context of the invention is a superposition of two spatial directions, thereby producing circular or elliptical motion in at least one plane in three-dimensional space. The oscillation generator can be a tubular oscillator or a rotor oscillator, in particular a piezoelectric oscillator. Longitudinal oscillations or flexural oscillations can be combined and superimposed. The invention is not limited to the type of oscillation generator or the particular oscillation direction, or to a particular oscillation frequency. It is important, however, that an improved polishing result can be obtained with the additionally generated oscillation.

In general, the tooth flank polishing tool can also be used to polish a thread. Threads have a tooth-like shape with tooth flanks, so that these can also be polished using the tooth flank polishing tool.

The invention will be described hereinafter in more detail with reference to exemplary embodiments depicted schematically in the drawing. It is shown in:

FIG. 1 a tooth flank polishing tool in form of a polishing disk;

FIG. 2 a cross section through the polishing disk of FIG. 1 according to a first embodiment;

FIG. 3 a cross section through the polishing disk of FIG. 1 according to a second embodiment;

FIG. 4 a tooth flank polishing tool in form of a polishing worm gear;

FIG. 5 a cross section through the polishing worm gear of FIG. 4 according to a first embodiment;

FIG. 6 a cross section through the polishing worm gear of FIG. 4 according to a second embodiment;

FIG. 7 a tooth flank polishing tool in form of a polishing finger;

FIG. 8 a cross section through the polishing finger of FIG. 7 according to a first embodiment; and

FIG. 9 a cross section through the polishing finger of FIG. 7 according to a second embodiment.

FIG. 1 shows in a simplified schematic diagram a tooth gear 1 and a tooth flank polishing tool 2 in form of a polishing disk, which are jointly clamped in an un-illustrated tooth flank polishing machine. The tooth flank polishing tool 2 has a base 4 rotating about a central axis 3. The central axis 3 can be moved by the tooth flank polishing machine in two different radial directions 5, 6. The polishing disk 2 is driven with a defined angular velocity and pressed with a likewise defined pressing force against the tooth gear 1. A polishing fleece 15 is attached on the base 4. The polishing fleece 15 engages in a tooth gap 7 of the tooth gear 1 and has in the section where it makes contact with a tooth flank 8 an outside contour that matches the shape of the tooth flank 8 of the tooth gear 1. The tooth gear 1 is clamped in the tooth flank polishing machine for rotation about its longitudinal axis 9. Accordingly, one tooth flank 8 after another tooth flank 8 of the tooth gear 1 can be polished.

FIG. 1 also shows schematically an oscillation generator 95 which is coupled to the base 4 in a manner that is not illustrated in detail. More particularly, the oscillation generator is a piezoelectric ultrasound motor which superimposes an oscillatory motion on the rotary motion of the base 4 or of the polishing fleece, wherein the oscillatory motion can point longitudinally in one of the illustrated spatial directions x, y, z or any other additional spatial direction. Longitudinal oscillations can also be superimposed, resulting in a rotation oscillation in an arbitrary spatial plane. The oscillatory motion of the base improves the polishing efficiency of the tooth flank polishing tool of the invention.

FIG. 2 illustrates the polishing disk 16 in cross-section. The base 4 having an inner cylindrical hollow space 10 is rotationally symmetric with respect to its central axis 3 and has on the radially outward peripheral side 11 a circumferential groove 12 in which the polishing fleece 15 is inserted. It can be seen that the polishing fleece 15 has on two surfaces 13, 14 an outside contour that matches the shape of two adjacent tooth flanks 8 (see FIG. 1). The polishing fleece 15 includes an organic material, for example cotton or sisal.

Another embodiment of the polishing disk 17 is illustrated in FIG. 3 in cross-section. Unlike in the polishing disk 16 (see FIG. 2), at the base 23 a circumferential bead 18 is formed, with a polishing fleece layer 20 applied on its radially outside 19. The bead 18 has an outside contour formed by two surfaces 21, 22 and matching the shape of adjacent tooth flanks 8 (see FIG. 1).

FIG. 4 shows schematically a tooth gear 30 and a tooth flank polishing tool 31 in form of a polishing worm gear, which are jointly clamped in an unillustrated gear hobbing mill. The tooth flank polishing tool 31 includes a base 32 on which once more a polishing fleece 33 is attached. The base 32 is supported for rotation about its central longitudinal axis 34 and can be moved by the gear hobbing mill in two different directions 35, 36. The polishing worm gear 31 is driven with a defined angular velocity and is pressed with a likewise defined pressing force against the tooth flanks 37 of the tooth gear 30. Like in the tooth flank polishing machine according to FIG. 1, the tooth gear 30 is clamped in the gear hobbing mill for rotation about a central axis 38.

The polishing fleece 33 engages simultaneously in several adjacent tooth gaps 39 of the tooth gear 30. In this exemplary embodiment, the polishing worm gear 31 has a tooth 40 which protrudes from the radially outward peripheral side of the base 32 and winds in a helical pattern about the base 32. The outer contour of the tooth 40 matches the shape of the tooth flanks 37 with which it is in contact. The tooth gear 30 rotates about its longitudinal axis 38 in unison with the rotation of the polishing worm gear 31. In this way, all tooth flanks 37 can be polished in a continuous process.

FIG. 5 shows a cross-section through a polishing worm gear 51 according to a first embodiment. As shown, the base 53, which has an interior hollow space 52, includes on its radially peripheral side 54 a groove 55 which winds around the base 53 in a helical pattern and into which the polishing fleece 56 is inserted. The polishing fleece 56 forms the tooth 40 (see FIG. 3) of the polishing worm gear 51. The polishing fleece 56 has an outside contour 57 that matches the shape of the tooth flanks 37 (see FIG. 3). The polishing fleece 56 includes a synthetic material, for example resin fibers, tangled resin fibers or nylon.

FIG. 6 shows a second embodiment of the polishing worm gear 58 in cross-section. Unlike in the preceding embodiment (see FIG. 4), the tooth 59 is formed on the base 53, and a polishing fleece layer 60 is applied on the tooth 58. The polishing fleece layer 60 is attached on the base 53 with an adhesive and includes a mineral material, for example aluminum oxide (Al₂O₃), preferably in form of corundum.

FIG. 7 shows a tooth flank polishing tool 70 in form of a polishing finger and a simplified schematic diagram of a tooth gear 71, which are jointly clamped in an unillustrated rotary table. The polishing finger 70 has a base 72 on which a polishing fleece 73 is attached. The polishing finger 70 rotates about its longitudinal axis 74 during polishing and is also adjustable in the direction of the longitudinal axis 74 of the polishing finger and the longitudinal axis 75 of the tooth gear. The polishing finger 70 is inserted in a tooth gap 77 and pressed with a predefined pressing force against (the) tooth flanks 76 to be polished and is guided in a translational motion parallel to the longitudinal axis 75 of the tooth gear along the surfaces of the tooth flanks 76.

FIG. 8 shows in cross-section a polishing finger 80 according to a first embodiment. The polishing finger 80 has a base 81 on which a shaft 82 is formed as a single piece. A seat 84 for a polishing fleece 85 is provided on the end 83 opposite the shaft 82. The polishing fleece 85 is held with a rotation lock in this seat 84. The base surface of the seat 84 and of the insertion section 86 of the polishing fleece 85 are hereby shaped as a polygon. The outside of the polishing fleece has a conical contour 87 that matches the shape of the tooth flanks 76 (see FIG. 7) with which the contour 87 makes contact. The polishing fleece 85 is made of nylon.

The embodiment illustrated in FIG. 9 shows another configuration of the polishing finger 90. Unlike in the embodiment of FIG. 8, the base 91 has a polishing cone 92. A polishing fleece layer 94 is applied on the outside 93 of the polishing cone 92. The polishing fleece layer 94 includes tangled resin fibers.

The polishing fleeces 16, 51, 80 of the embodiments illustrated in FIGS. 2, 5 and 8 are shown as a single piece. However, these polishing fleeces could also be produced with a stiffening core made of a different material, wherein the polishing fleece is arranged only on the outside of this core.

LIST OF REFERENCES SYMBOLS

1 Tooth gear 2 Tooth flank polishing tool 3 Central axis of 4

4 Base

5 Radial direction 6 Radial direction

7 Tooth gap

8 Tooth flank 9 Longitudinal axis of 1 10 Hollow space 11 Peripheral side of 4

12 Groove

13 Outer surface of 15 14 Outer surface of 15 15 Polishing fleece 16 Polishing disk 17 Polishing disk

18 Bead 19 Outside of 18

20 Polishing fleece layer 21 Outer surface of 20 22 Outer surface of 20

23 Base

30 Tooth gear 31 Tooth flank polishing tool

32 Base

33 Polishing fleece 34 Central axis of 32 35 Radial direction 36 Radial direction 37 Tooth flank 38 Longitudinal axis of 30

39 Tooth gap 40 Tooth

51 Polishing worm gear 52 Hollow space

53 Base

54 Peripheral side of 53

55 Groove

56 Polishing fleece 57 Outside contour of 56 58 Polishing worm gear

59 Tooth

60 Polishing fleece layer 70 Polishing finger 71 Tooth gear

72 Base

73 Polishing fleece 74 Longitudinal axis of the polishing finger 75 Longitudinal axis of the tooth gear 76 Tooth flank

77 Tooth gap

80 Polishing finger

81 Base 82 Shaft 83 End of 81 84 Seat

85 Polishing fleece 86 Insertion section

87 Contour

90 Polishing finger

91 Base

92 Polishing cone

93 Outside of 92

94 Polishing fleece layer 95 Oscillation generator 

1.-18. (canceled)
 19. A tooth flank polishing tool comprising: a base rotatable about a central axis, and a polishing fleece attached to the base and configured for insertion in at least one tooth gap of a tooth gear to be polished, the polishing fleece including at least one section with an outside contour that matches a shape of a tooth flank of the tooth gear.
 20. The tooth flank polishing tool of claim 19, wherein the polishing fleece comprises an organic material, a synthetic material or a mineral material, or a combination thereof.
 21. The tooth flank polishing tool of claim 20, wherein the polishing fleece comprises cotton or sisal.
 22. The tooth flank polishing tool of claim 20, wherein the polishing fleece comprises resin fibers, tangled resin fibers or nylon.
 23. The tooth flank polishing tool of claim 20, wherein the polishing fleece comprises aluminum oxide (Al₂O₃).
 24. The tooth flank polishing tool of claim 19, wherein the polishing fleece is applied at least over sections of a surface of the base.
 25. The tooth flank polishing tool of claim 19, wherein the polishing fleece is strung over a surface of the base.
 26. The tooth flank polishing tool of claim 19, wherein the base comprises a radial circumferential groove or a seat, and the polishing fleece is inserted in the radial circumferential groove or the seat.
 27. The tooth flank polishing tool of claim 19, wherein the base and the polishing fleece in combination are shaped as a polishing disk.
 28. The tooth flank polishing tool of claim 19, wherein the base and the polishing fleece in combination are shaped as a polishing worm gear.
 29. The tooth flank polishing tool of claim 28, wherein the polishing fleece forms a tooth.
 30. The tooth flank polishing tool of claim 19, wherein the base and the polishing fleece in combination are shaped as a polishing finger.
 31. The tooth flank polishing tool of claim 19, further comprising an oscillation generator which is at least indirectly coupled to the base.
 32. The tooth flank polishing tool of claim 31, wherein the oscillation generator produces an ultrasound oscillation.
 33. A method for polishing a tooth flank of a tooth gear with a tooth flank polishing tool having a base rotatable about a central axis and a polishing fleece attached to the base, the method comprising the steps of: inserting the polishing fleece in at least one tooth gap of a tooth gear to be polished, with the polishing fleece including at least one section having an outside contour that matches a shape of a tooth flank of the tooth gear, and rotating the base with the attached polishing fleece in the tooth gap.
 34. The method of claim 33, wherein the tooth gears have a diameter of greater than 1000 mm.
 35. The method of claim 33, further comprising the step of superimposing on the rotary motion of the base an oscillatory motion in at least one spatial direction.
 36. The method of claim 33, wherein the tooth gear is a thread. 